Internal-combustion engine



May 4, 1948. [PROBST 1 2,440,726

INTERNAL-COMBUSTION ENGINE Filed Oct. 15, 1945 4 Sheets-Shet 1 l I 1 1 I l I I l r I l INVENTOR. I Karl /f. 3 352.

INTERNAL-COMBUSTION ENGINE Filed Oct. 15, 1945 4 Shegts$heet 2 May 4, 1948. PROBST 2,440,726

INTERNAL-COMBUSTION ENGINE Filed Oct'. 15, 1945 4 Sheets-Sheet 3 INV.ENTO.R.

fizz/Z K 777252? Patented May 4, 1948 UNITED STATES PATENT OFFICE 2,440,726 I INTERNAL-COMBUSTION ENGINE Karl K. Probst, Lansing, Mich.

Application October 15, 1945, Serial No. 622,261

' Claims. (oi. 123-71) This invention relates to internal combustion engines, and particularly to those of the twocycle type, the principal object being the provision of an engine of this type that is efilcient and economical in operation.

Objects of the invention include the provision haust and an intake port in a wall thereof at least partially controlled by movement of the corresponding piston and in which it is possible to positively supercharge the engine; the provision of a two-cycle engine having a novel timing of the ports thereof; the provision of a two-cycle engine of the differential piston type in which the larger portion of each piston acts to positively pump the air required for supporting combustion in the corresponding cylinder; the provision of an engine of the type above described in which a rotary valve is provided for controlling the passage of the air pumped by the larger diametered portion of the piston to the engine power cylinder; the provision of a construction as above described in which the rotary valve not only serves to aid in the control of the passage of such air to the combustion chamber, but

serves as a temporary storage chamber for the air so compressed; the provision of a construction as above described in which the rotary valve, in a multi-cylindered engine, individually stores the air pumped by each piston for use in the corresponding cylinder; and the provision of a two-cycle engine having a rotary valve for controlling passage of air to the engine cylinders for supporting combustion therein, which operates at only a fraction of the crank shaft speed.

The above being among the objects of the present invention, the same consists in certain new and novel features of construction and combinations of the parts to be hereinafter described with reference to the accompanying drawings, and then claimed, having the above and other objects in view.

In the accompanying drawings which illustrate a suitable embodiment of the present invention and in which like numerals refer to like parts throughout the several different views,

Fig. 1 is a partially broken, partially sectioned,

side elevational view of a two cylinder, two-cycle engine embodying the present invention.

Fig. 2 is a transverse, vertical sectional view of the engine shown in Fig. 1, taken as on the line 2-2 thereof.

Fig. 3 is a fragmentary transverse sectional view taken on the line 3-3 of Fig. 1 in the plane of the passage connecting the carburetor with Fig. 8 is a. side elevational view of the rotary valve employed in the engine shown in the preceding views. 7

Figs. 9, 10, and 11 are transverse, sectional views of the valve shown in Fig. 8, taken, respectively, on the lines 9-9, Ill-Ill, and ll-ll of Fig. 8, and

Fig. 12 is a port diagram for the engine shown in the preceding views.

It is generally understood that two-cycle engines, as compared to four-cycle engines, have the advantage of much greater simplicity in con-' struction and economy in manufacture, but have the disadvantage of lesser flexibility and poorer fuel economy. The present invention has for its principal object the provision of a two-cycle engine retaining the advantages thereof as far as simplicity in construction and economy in manufacture are concerned, but capable of flexibility and fuel economy approaching, if not equalling,

that of a four-cycle engine. Briefly, it may bestated that these advantages are obtained by eliminating base compression and employing a differential piston for each cylinder for delivering to the power cylinder portion thereof the charge of air necessary to support combustion, and by providing a rotary valve which, in conjunction with the piston controlling the port of each cylinder, controls the delivery of such combustion supporting the air to the power cylinder. The rotary valve, in accordance with the present invention, not only aids in' controlling the admission of the combustion supporting air to each 'power cylinder of the engine but additionally serves as a storage chamber for the air compressed by each differential piston in the corresponding pumping cylinder of the engine between the time such charge is fully compressed and the time it is desired to introduce it into the power cylinder. In this'last connection, it will be understood that in accordance with the present invention the valve is so formed that when applied to a multi-cylinder engine the charge of air compressed by each piston is delivered only to the power cylinder in which such piston operates, rather than delivery to a storage chamber common to all of the cylinders, this feature resulting in a higher initial pressure of such combustion supporting air at the moment it is initially introduced to its power cylinder, permitting the charge to .be introduced into the power cylinder in a shorter length of time than otherwise and providing for improved performance in control. Furthermore, this feature lends itself to a piston controlled cylinder porting by means of which a positive supercharging of the engine may be provided.

Additionally, in the interest of long' wear and greater life, the rotary valve is driven at only a fraction of the crankshaft speed, preferably onehalf such speed. While rotary valves employed in four-cycle engines are naturally driven at halfengine speed, this feature has been an inherent result-of the four-cycle principle and in such caseeach port in the valve registers with the corresponding port in the cylinder as often as explosions occur in the corresponding cylinder,

while in the present case a double set of ports are provided in the rotary valve for each cylinder which alternately align themselves with passages two upwardly projecting parallel cylinders indicated generally at 22, each of which is provided with an integral cylinder head portion each of which receives a spark-plug 24 in the conventional manner. Cooling fins 26 are formed integrally with each cylinder 22. The lower open face of the crankcase is closed by an oil pan 28 which is generally of the nature of the oil pans conventionally employed in connection with fourcycle engines, this being differentiated from the conventional type of two-cycle engines employing base compression in which the lower and upper halves of the base are made to relatively lit in the cylinder so that each port provides a passage for the fiow of gases corresponding with every other explosion in the corresponding cylinder. By this means the speed of the rotary valve is reduced to such extent, as compared to the speed of the crankshaft, as to prevent it from. presenting any unusual cooling problems, and at the same time materially increasing its length of life as compared to the life it would have if run at crankshaft speed.

It will, of course, be appreciated that the engine constructed in accordance with the present invention may carburete the air employed for supporting combustion in the engine cylinder in any suitable manner. In other words, the air may be carbureted before being introduced into the engine,. as by acarburetor, not untiiit has been introduced into the power cylinder of the engine, as by. fuelinjection, or at any suitable point in the path of flow of the air from the intake port in the engine to the power cylinder by any means whatsoever. As a matter of illustration, it is assumed in the particular embodiment illustrated in the drawings by way of illustration that the air'is carbureted in the first described mannennamely, by passing through a carburetor' of conventional construction beforebeing introduced'into the engine.. It will also be'understood thatthe present invention is applicable to engines. having one cylinder or any number of cylinders, the particular engine shown inthe'drawing by-way of illustration being. shown as having two cylinders. Furthermore, it will be understood that the engine of the present invention may be'cooled'in any suitable .way, whether'by air, water,.or other fluid,

medium.- The engine shown in theaccornpany- I ing. drawings by way of illustration is of the aircooledgtype.

Referring now to the accompanying drawings andparticularl'y tor'Figs. 1. and 2, the engine there shown comprises a crankcase 20 of cast construction with which is integrally formed.

'throw crankshaft 32, the throws of which are angularly spaced from one another by 180. Each of the-throws of the crankshaft rotatably receives thereon the big end of the corresponding connecting rod 34, the upper end of the connecting rods being connected to their corresponding pistons which will now be explained. A flywheel 36 is secured to the rear end of the crankshaft 32 and carries a centrifugal fan 38 which draws air through the sheet metal housing 39 surrounding the cylinders 22 in order to cool the latter.

Referring now particularly to Fig. 2, it will be noted that each cylinder 22 is bored to provide an outer cylindrical portion and a concentric inner cylindrical portion d2 of greater diameter.

For the sake of convenience, the portion 40 will hereinafter be referred to as the outer, power or working cylinder and the portion d2 as the inner or pumping cylinder. A difierential piston indicated generally at 44 is received in each cylinder 22 and each comprises anouter portion it relatively closely, but slidably fitting the bore of the working cylinder 40 in accordance with conventional practice and an inner portion 48 relatively closely, but slidably fitting the bore of the inner cylinder t2, the two portions 46 and 48 being formed integrally with one another and the corresponding connecting rod 34 being connected to the smaller portion 46 in each case by means of a conventional piston pin 50. of the connecting rods are such in relation to the lengths of the pistons that a minimum of clearance is provided above the pumping piston at upper dead center position. v

The head of the working piston 46 is shown as being provided with a conventional deflector or baflle -52 for directing the incoming charge of air upwardly into the cylinder 40 in accordance with conventional practice, but itwill be understood in this respect that the head of such pistonmay vary considerably in conformation opposite the baflle 52, but hereagain the shape of the outer end of' the cylinder, which forms t the combustion chamber therefor, may vary in each casein accordance with the necessities o desires of the particular designer. 3 r r As will be appreciated, the construction The lengths and the pumping cylinder 42. By varying the relative diameters of the cylinders 40 and 42 and the corresponding piston portions 48 and 48, the effective swept volume .of the cylinder 42 may be made to equal that of the cylinder",

I or greater or lesser-than the latter. Ordinarily,

it will be desirable that the swept volume of the pumping cylinder be somewhat greater than that of the working cylinder in order to make up for any loss in volumetric efficiency of the engine, which loss-may result from friction to the flow of gases through the various ports and passages which will hereinafter be described, and for other well known reasons.

Additionally, where maximum power at high engine speeds is particularly desirable at the possible risk of less desirable economy at low engine speeds, the relative diameter of the pumping piston 48 with respect to the working piston 40 may be desirably increased to insure better volumetric efficiency of the working cylinder at such high speeds, and if suficiently increased, a positive supercharging eifect may be obtained. In all such matters, of course, the requirements of the particular design being worked upon and the intended application of the final product will control.

The discharge of exhaust gases from the working cylinder is controlled by the piston in accordance with conventional two-cycle practice. In other words, each working cylinder 60 is provided at one side thereof with one or more exhaust ports 52 which are uncovered by the corresponding working piston to when the latter approaches its bottom dead-center position. and

which ports 52 discharge through a common outlet such as Ed into an exhaust manifold 50, or the exhaust gases may be discharged directly to the air if desired. It may be noted, however, in the case shown and, as particularly brought out in Figs. 3, 4, and 12, each piston M will uncover the corresponding exhaust port at approximately 45 before bottom dead-center position and will, of course, close it the same number of degrees past bottom dead-center position.

In accordance with, the present invention, the control of combustion supporting air to the working cylinder ll and the discharge therefrom to the working cylinder til is controlled by a rotary valve which is indicated generally at M. In order to mount the valve 60, a hollow boss til is formed integrally with both cylinders 22 and extends along one side thereof, as shown, with its axis parallel to the axis of the crankshaft 32. The boss 62 is provided with a cylindrical bore 03, in which the valve $0 is closely but rotatably received. It will be particularly noted from inspection of Fig. 1 that the forward or left-hand end of the boss 62 is outwardly flanged and has secured and sealed thereto a flat, vertically ex tending plate M which is also sealed and secured to the forward end of the crankcase fill and oil pan 28. The forward end of the valve 60 projects through the plate 64 and receives a gear 66 thereon which is suitably secured thereto against relative rotation. In vertical alignment with the gear 66, the crankshaft 32 is provided with a gear 68 fixed against rotation thereto. The pitch diameter of the gear 68 is half that of the gear 66.

The two gears 88 and 68 are drivingly interconnected by means of an idler gear 10 suitably mounted on a stubshaft 12 carried by the plate 84. All of the aforementioned gears are enclosed by an oilproof sheet metal housing 14 of more or less pan-like construction, the open outwardly flanged margin of which is suitable secured and sealed to the marginal edge portion of the plate 640. The housing I4 is, of course, provided with a suitable opening through which the forward end of the crankshaft 32 projects. It will be appreciated from the foregoing that the valve 80 will be rotated at half the speed of the crankshaft 32. From inspection of Fig. 1, it will also be noted that the rear or right-hand end of the boss 62 is closed by a plug I6 which substantially abuts the rear end of the valve .60.

Referring now to Fig. 8, which is -a side elevational view of the valve 60, it will be noted that the valve includes two consecutive axial portions A and B, each of which serves a corresponding cylinder 22 to control the flow of combustion supporting air into the corresponding pumping cylinder 42, and from the corresponding pumping cylinder 42 to the corresponding working cylinder.

. 40. Inasmuch as the portions A and B are identical to each other, except angularly rotated with respect to each other, the construction and function of one will sufiice to explain the construction and function of both. Each portion A and B includes a portion which controls the flow of combustion supporting air from the atmosphere to its corresponding pumping cylinder t2, a portion 82 which controls the escape of such combustion supporting air from each pumping cylinder 42, and a portion 84. which controls the flow of such combustion supporting air to the corresponding working cylinder 40. Each portion A and B is formed within the corresponding portions 82 and 84 thereof with an axial bore 86 forming a pocket, such pockets 86 being formed in the particular case shown by drilling the valve 60 from opposite ends thereof and plugging the outer ends of the holes thus formed as by means of plugs 88 to form two axially distinct and separate pockets 86, one for each portion A and B. Circumferential grooves 90 are provided in the valve 60 between each adjacent portion 80, :02, and 84, and sealing rings 92. are received in each groove 90 for cooperation with the bore 63 in order to seal each of said portions against the escape of gas between them.

As brought out in Fig. 3, the boss 82 in transverse alignment with each portion 80 is provided with a radially extending passage 9 3 which passages are interconnected by a longitudinally extending passage 90 formed in an intake manifold portion 98 which in turn opens into a carburetor I00 which may be of a conventional type. Thus, the carburetor I00 through the passage 96 may supply a combustional mixture to both passages 9t. Likewise, each cylinder 22 in transverse alignment with its corresponding valve portions 80 is provided with a passage I02 which connects the bore 6310f the boss 62 with a port I04 opening into the corresponding pumping cylinder M on the corresponding side of a plane perpendicular to the axis of rotation of a crankshaft and including the axis of the corresponding cylinder.

As brought out in Fig. 3, each portion 80 of the valve 60, and on diametrically opposite sides thereof, is cut away as at I06 to provide a flow passage or port operable to interconnect the passages 94 and I02 when the valve is within either of two diametrically opposite positions of angular movement. Each port or passage Ill-6 is of such sponding passages-Stand I02 'will be opened during'operation to each other through thethen cooperating port or passage I86 when the corresponding crank pin-oi the crankshaft 82 is apangular extent in. its relation to relative angular positions and extent of the passages 94 and I82 that, as brought out inFigs. and12, the correproximately 60 past dead center, .and'will close 0 communication between the corresponding ports .94 and 102 when such corresponding crankpin has-passed beyond bottom dead center positionby approximately 40 It will, of course, be un- .derstood that during one down stroke of apiston,

,one oi the corresponding ports 186. will control I the flow of combustional mixture through the I carburetor 108 into the corresponding" pumping cylin'der'42, while on the next downward stroke of the piston the-remaining corresponding port I06 will control such 'flow.

As best brought out in Fig.6, each cylinder 22 in line'with the corresponding portion 82of the valve 68, and which is on the opposite side of the central plane abojve referred to including the axis of each cylinder from the corresponding port I04,

is provided with a port 88, similarto the port I84, and whichis connected by a passage III! with the bore 83 of-the boss s2." The-portion'82 of the corresponding portion- A MB of thelvalve 60 in transverse alignment therewith is provided with a pair .of diametrically opposed ports H2 throughthe wall'thereof. The angular extentof the ports H2 in relation to the angular extent'of .the passages H0 abo'utjthe axis of -rota'tionof the valve 60, and, therelative rotatable position of the valve 60 and crankshaft 32 is such that, as best brought out in Figs. 6 and'12, one of the ports I l2 begins to-open into its corresponding passage H0 its upper dead center position, at which time the explosion occurs in the corresponding working cylinder. Consequently, it is necessary to hold such-charge in the corresponding pocket 88 until the corresponding working piston has approached its bottom dead center position and the pressure of the exhaust gases in materially dissipated. 1

In order to control the discharge of suchcompressed gas in each pocket 86 to the corresponding working cylinder 48, each portion 84 of the valve 68 is provided with a pair of diametrically i. opposed ports H4 therein connecting the corresponding pocket 86 with'the periphery of .the

' combustionin the corresponding-working cylin-v .port H6.

portion; Each working-portion 48 ofthe cylinder 22 is provided with a port H6 connecting the bore of the corresponding cylinder with the bore 63 in'which the valve 60 rotates. Now it will" be observedfrom an inspection of Figs. 2 and '1 the cylinder has been i It will be appreciated that if the ports'lfl were aligned-with the ports H6 at the time the 'corresponding workin g piston 46 uncovered the corresponding intake. port I Hi,v the products of -the der might be. under a .pressure superior to the I pressure of the charge ot'air or combustible mix- .1 ture in'thecorresponding pocket 86, and tend to when 'thecorresponding crank'pin is approxi-y,

*mately past bottom dead center position, and -closes such' communication when such pin is ap roximately 10? past 'dead center position.

During thev greater part of this time, the piston .48 in the corresponding cylinder 42 is moving outwardly and compressing the charge which it:

drew into the cylinder 42 .on its down stroke, and

responding working (cylinder? 40, but is compressed and held in-such passage 86.; Each pocket blow into 7 such pocket. In order to avoid any i such occurrence and to insure the pressure of the. burned gases inthe working cylinder to be largely dissipated-at the time the ports. H4 become aligned with the intake'iport H6, the ports H4 are=so angularly related to the valve 68 and the 1 crankshaft 32 that the ports H4 do-not begin to open' to' the ports -I I6 until, as brought out in the timing diagram of Fig .-1 2, the correspond,- ing crankpin has reached a position of approximately=15 past'bottom dead center. It will'be appreciatedithatby time the pressure of is compressing such'charge into the corresponding pocket 86 of the valve 68. {This charge, as f will hereinafter be brought out more clearly, is not immediately allowed to escape to the cor- 86, being of materially smaller volumethan the volume in 'the corresponding 'cylinder42fswept by the corresponding piston 48, the charge thus 1 compressed. thereinis under a material pressure,

depending upon the relation of the .volume of the pockets 86 as ,compare'd to'the swept volume of "the cylinders 42, but preferably. on the'order of thirty to forty pounds per square inch. It will be understood in this latter respect that this figure may-vary considerably according'to the desires of the particular designer and the efiect he isattempting to obtain. In any event, it will be appreciated that" this pressure is materially greater than is ever obtained in base compression types-of two-cycle engines and is-one feature by means of which superior operating characteris- I ties are obtainable by the present invention.

Itwill be appreciated that the reason why the I charge compressed by each piston 48 in its corresponding cylinder 42 cannot be immediately transferred from the pocket 8-6 to the corresponding working cylinder 40 is that such charge is passed approxinriately beyond bottom dead the burned gases in thefzcorresponding working cylinder will have been substantially dissipated through-the corresponding exhaust passage 52,. and may. have even created a partial suction in the working cylinder due to the inertia eiiect of such exhaust gasespassingthrough the exhaust In the construction as shown the interruption of the'alignment'of the ports H4 and H6 is not relied upon tojcut ofi'communication between each pocket "86lfand its corresponding working cylinder 48 as maybe arrangedif desired. In-- stead-the corresponding working piston 46 .it-

self is relied upon and employed to shutoff communications between each working cylinder 40 and the corresponding pocket 8t as it has been shown that by this means a more efiective' new path between each pocket 86 and its correspondingworking cylinder results, particularly toward the end of such communication.

I One feature which is to be noted from the timing diagram illustrated in Fig. 12 and resulting from the fact that the intake port H6 extends axially'outwardly beyond the upper end of the exhaust port 52, .a feature contrary to ported cylinder types of'two-cycle engines is that the intake port remains open after the exhaust port closes, namely until the corresponding crank has center position in the construction shown. This feature, particularly when combined with the construction in which the swept volume of the pumping cylinder 42 is greater than the swept volume of the power or working cylinder 40 will result in a positive supercharging effect for the engine, inasmuch as in such case the charge from the pocket is being delivered" to a closed space.

With the above in view and reviewing the sequence of operations as disclosed in the tim-'- ing diagram in Fig. 12 and in Figs. 4 to '7 inclusive, and having reference to a single cylinder of the engine only for the purpose of simplification in explanation, it will be appreciated that when the crankpin has turned approximately 60 beyond top dead center position, as indicated in Figs. 5 and 12, one of the passages or ports I06 in the portion 80 of the valve 60 establishes communication between the carburetor I00 and the pumping cylinder 42 through the ports or passages 94, I02 and I04. The piston 44 is moving downwardly at this time, thus creating a suction in the pumping cylinder 42 and draws a charge of combustible mixture into the pumping chamber. This communication between the carburetor and the pumping cylinder remains open until the crankpin has passed beyond bottom dead center position, preferably approximately 40 as indicater in the timing diagram of Fig. 12 and in Fig. 5, so as to insure a maximum amount of such combustible mixture being drawn into the pumping chamber, as will readily be appreciated by those skilled in the art. It will also be understood that when the piston has descended sulficiently to bring its corresponding crankpin to a position of approximately 45 from bottom dead center position, as indicated in Figs. 4 and 12, the piston will begin to uncover exhaust port 52 and permit the escape of the burned products of combustion in the power cylinder 40.

Immediately after communication between the carburetor and the pumping chamber is interrupted, as indicated in Figs. 6 and 12, one of the passages I M in the portion 82 of the valve Ml will open communication through the ports I08 and I Ill between the pumping chamber and the pocket 86 in the valve 60, and as the piston M continues to rise in the cylinder the charge therein will be compressed and forced into the pocket 86. This action will continue until the crankpin has preferably passed slightly beyond upper dead center position, shown in the timing diagram of Fig. 12 and in Fig. 6 at 10 past top deadcenter position. This lag in closing is, of course, for the same general reasons as the lag in closing the first mentioned port between the carburetor and the pumping cylinder. The lag in this case does not require to be extended to such a great degree in view of the relatively high pressure on the charge at this time.

'When thecommunication between the pump- .ng chamber and the pocket 86 of the valve fill :loses as above described, the pocket 86 is then :harged with substantially the entire volume of ;he charge of combustible mixture which has square inch has resulted in very satisfactory operation.

The charge remains compressed in the pocket 88 and, of course, the corresponding passages H4 until, as brought out in Fig. 7 and in the timing diagram of Fig. 12, the crankpin has passed 15 beyond bottom dead center position. This communication between the pocket 86 and the interior of the working cylinder 40 which opens at 15 past bottom dead center position continues until the crankpin has turned through an angle of approximately beyond bottom dead center position, at which time it is closed. The closing of this communication may be effected by rotation of the valve 60 so as bring the ports H4 and H6 out of registry with one another but, as previously described, it is preferable to cut all such communication by the piston 44 itself, the upper edge of the same passing beyond the upper edge of the port 6 in such case to cut off such communication. By this method of closing off such communication, a maximum amount of area of the port H6 remains open until the last moment and is important inasmuch as at the time such port is closed the pressure of the gases in the pocket 86 has dropped to a minimum amount, the value of which will depend upon the ratio of the swept volumes of the cylinders 40 and 42. Furthermore, because the pressureof exhaust gases in the working cylinder 40 has dropped to approximately zero at the time the pocket 86 is communicated with such cylinder, and because the charge in the pocket is under a material positive pressure, such charge will flow quickly and easily into the power cylinder. Additionally, because the exhaust gases have largely been cleared from the power cylinder when the charge from the pocket 861s introduced into it, a minimum of dilution of such charge by exhaust gases will occur.

It is important to note that although the intake port into the power cylinder is initially open at the same time that the exhaust port 52 is open, as in conventional two-cycle engines in whichthe movement of pistons controls the opening and closing of the port, in the present case the intake port is not open before bottom dead center position is reached as in conventional types of two-cycle engines and is only opened after the exhaustport has been uncovered for a material time element. Further, because of the fact that the intake port M6 extends axially outwardly beyond th outer end of the exhaust port 52, the exhaust port closes while the intake port is still substantially fully open. By this arrangement, the possibility of the loss of live gases through the exhaust port at lower engine speeds is substantially eliminated and, additionally, it provides a construction in which a positive supercharging effect may be obtained.

It will be appreciated from the foregoing description that the engine provided in, accordance with the present invention dispenses with base compression for delivering air for supporting the combustible charge to the engine cylinder, and that this not only permits a more conventional, emcient and economical oiling system of the type commonly employed in connection with fourcycle engines to be employed therewith, but ad- Furthermore, by introducing the air for supporting combustion in thepower cylinder into the power cylinder under a relatively high pressure as- ,described, better scavenging oi the burnt parts of the combustion from the power cylinder obtained, operating conditions are materially improved. fuel economy at lower'speeds is materially increased and a positive supercharging effect may be provided if desired, thus providing for a materially greater power output tor the same cubic contents of the cylinders at a given speed. 1 Having claim by Letters Patent is:

1. In a two-cycle engine of the class wherein a" differential piston works-in a diflerential cylinder and the smaller diameter portion oi. said piston controls the escape oi exhaust gases through a port in the wall oi'said cylinder, an inlet port in the wall of the smaller diameter portion of i 1 said cylinder covered and uncovered by movement 01. said piston in said cylinder, air for supportingcombustion being drawn into the larger diameter portion of said cylinder during movement of said piston toward bottom dead centerj position and compressed by said larger diameter portion during movement thereof toward top' dead center position, a discharge passage from said larger diameter portion of said cylinder leading to said inlet port, and arotary valve driven intlmed relationto said engine interposed in 'said discharged passage, the combination with 'said valve oi a pocket formed interiorly thereof and a port therein alternately communicating with that portion of said discharge passage leading thereto from said larger diameter portion of said cylinder and that portion of said discharge passage leading therefrom to said inlet port, the

"entire power stroke oi. said piston whereby to hold said air compressed in said pocket during such time, said valve moving to open said port to that portion of said passage leading to said inlet port during the initial movement of said piston from bottom dead center position toward top dead center position without opening communication between said pocket and that portion oi said .thus described my invention, what I y f passage'leading to said larger diameter portion of said cylinder, and movement of said piston in said cylinder serving to interrupt communication I between said, pocket and said inlet port during the last mentioned movement 01 said piston.

In a two-cycle engine of the class wherein a differential piston works in a diflerential cylinder and the smaller diameter'portion of said piston controls the escape of exhaust gases through a port in the wall of said cylinder, an inlet port in the wall of thesmaller diameter portion of said cylinder covered and uncovered by movement of saidpiston in said cylinder, air ior supporting combustion being drawn into the larger diameterportion of said cylinder during movement of said piston toward bottom dead center position and compressed by said larger diameter portion during movement thereof toward top dead center position. a discharge passage, from b said larger diameter portion of said cylinder leading to said inlet port, and a rotary valve driven in timed relation to said engine interposed in said discharged passage, the combination with said portion of said discharge passage leading thereto from said larger diameter portion-oi'said cylinder and that portion 01 saiddischarge passagelead- ,ing therefrom to said'inlet port, the rotary Desirotary position of said valve closing said port therein to both, portions or said passage during substantially the, entire power stroke of said pisr ton whereby to hold said air compressed in said 2. In a two-cycle engine of the class wherein a differential piston works in a diil'erential cylinder I "V and the smaller diameter portion of said piston valve of a pocket formedinteriorly thereof and a port therein alternately communicating with that tionof said valve closing said port therein to both portions of said passage during substantially the entire power stroke of said piston whereby to hold said air compressed in said pocket during such .time,'said valve movingto open said port to that portion of saidpassage' leading tosaid inlet port. during the initial movement of said piston from bottom dead center position toward top dead center position without opening communication between said pocket and that portion-oi said passage leading to said larger diameter portion of said cylinder, and said communication between said pocket and said smaller diameter portion of controls the escape of exhaust gases through'a 7 port in the wall or said cylinder, an inletport in' the wall of the smaller diameter portion of said cylinder covered'and uncovered by movement of said piston1in. said cylinder, air'ior supporting portion of said cylinder during movement of said piston toward bottom dead center position and is compressed by said larger diameter portion during movement thereof toward top dead center position, a discharge passage from said larger relation to said engine interposed'in saidv discharged passage, the combinationwith said valve.

of a pocket formed interiorly thereof and a port tion of said discharge passage leading thereto said cylinder through said" inlet port continuing latter the last mentionedmovement of said piston has closed. the first mentioned port.

4. In a two-cycle engine of the class wherein a piston working in a cylinder controlstheescape of exhaust-gases through a port in the cylinder combustion being drawn into the larger diameter I diameter portion of said cylinder leading to said a inlet port, and a rotary valve driven in timed wall, a port in the cylinder wall covered and uncovered by movement of the piston is provided for the introduction of combustion supporting air to the cylinder; the piston being connected to a crankshaft by means of a connecting rod for converting reciprocatory movement of the piston to rotary movement of said crankshaft, and means provided for compressing said air for delivery through said last mentioned port, of means operated in timed relation to said engine for ren- .'d'ering said last mentioned port inoperative to therein alternately communicating with that porfrom said larger diameter portion of said cylinder and that portion of said discharge passage leading therefrom to said inlet port, the rotary position of said valve closing said port therein to both l portions'oi said passage during substantially the deliver said compressed air to said cylinder until said piston has uncovered the first mentioned port and has substantially reached bottom dead center position, comprising a rotary valve interposedin the path of flow of said compressed an to said last mentioned port, said'valve having a pair of diametrically oppo'sed ports thereir alternately operative to permit said ilowot said compressed air therethrouah to said last mentioned port durina'rotation of said valve, and means operatively interconnecting said valve to said crankshaft for receiving driving movement therefrom operable to drive said valve at one half the speed of rotation of said crankshaft.

5. In an internal combustion engine of the class including a cylinder, a piston reciprocable in said cylinder, a crankshaft and a connecting rod interconnectingsaid crankshaft and piston, the combination with said engine of means driven thereby for compressing a charge of combustion supporting airsaid engine having a passage between said means and said cylinder, a rotary valvc driven by said engine in timed relation 0! one revolution of said crankshaft at which time the other of said ports is not aligned with that portion of said passage leading to said cylinder, and said other or said ports being aligned with the first mentioned portion of said pasiiage.-

KARL 11 P110381.

I nsraaancas err-an The following references are of record in the tile of this patent:

v UNITED STATES PATENTS Number Name x Date 1,099,065 Leech June 2, 1914 1,176,951 Fornaca Mar. 28, 1918 1,239,224 Rudquist Sept. 4, 1917 1,299,895 Anderson Apr. 8; 1919 1,304,443 Belyavin et al. May20; 1919 1,530,390 Micklewood Mar. 17, 1925 1 1,677,057 Streeter July 10,1928

, FOREIGN PATENTS Number Country Date 493,727 Great Britain 1938 553,965 Great Britain 1943 

